NeuroScience

As succinctly as possible: Brain activation patterns during the first test or recall of "studied pairs predicts performance on the second test." Importantly, while subsequent memory analyses of encoding trials also predict later accuracy, the brain regions involved in predicting later memory success are "more extensive for activity during retrieval (testing) than during encoding (study). Those additional regions that predict subsequent memory based on their activation at test but not at encoding may be key to understanding the basis of the testing effect (Liu et al., 2014).

Regions in prefrontal and parietal cortex and medial temporal lobe (MTL) consistently emerged Liu et., (2014) analyses and these regions have been associated with conceptual and attentional processes and memory storage, all of which are required for successful learning. Specifically, researchers were observing the differences between subsequent memory effects for encoding and retrieval subsequent memory effects to explain why testing is superior to study.

Liu et al., (2014) also prompted our awareness of response time and the acceleration of correct recalls with subsequent correct retrievals. An observation we had also noticed in field settings.

Correct recalls in Test 2 were significantly faster than at Test 1, (in part greater task familiarity with the task interface) though not accelerated when correct at Test 2 vs. incorrect at Test 2.

Predefined fMRI analysis: Could brain activity during retrieval (testing) predict subsequent memory performance?

Liu et al., (2014) reported that while being correct on the first cued recall test did not guarantee correct recall on the second test, the activation values in brain activation on the first successful recall did predict whether the second attempt would also be correct. (Of six brain regions measured significant correlations were observed in right Prefrontal Cortex (PFC) (r = .64, p = .022) and right Posterior parietal cortex (PPC) (r = .57, p = .012) Activations in the other 4 regions were also positively correlated with behavioral performance on Test 2 although not statistically reliable (left PFC: r = .37, left PPC: r = .42, left hippocampus: r = .17, right hippocampus: r = .11). Brain regions that were more active during testing than during restudying.

Furthermore Wing et al. (2013) and van den Broek et al. (2013), regardless of the modified recall method, reported that same brain regions emerged during successful retrieval (on the intermediate tests). In the van den Broek et al. (2013), significantly better and faster for tested words than for restudied words. Conceivably, the activation of right PFC during retrieval is responsible for stronger association formation and better learning than what typically occurs during study.

van den Broek et al. (2013), identified enhanced activity in inferior frontal gyrus (IFG) during testing than restudying, repeatedly related to intentional, non-automatic processing in memory studies. Higher activation during testing than during restudying therefore supports the idea that testing involves more intentional, effortful processing than restudying, but as such, was not predictive of better memory retention.

Does learning during testing differ from learning during study?

Significant subsequent memory effects were found in left Prefrontal Cortex and bilateral hippocampus, left, t(14) = 2.66, p = .01; right, t(14) = 2.12, p = .027.There were no significant effects in right PFC or right PPC, t's <1.

In summary:

Both the Regions of Interest (ROI) and the whole brain exploratory analysis revealed that the brain regions previously identified as responsible for learning during study, namely the left PFC, left PPC and hippocampus were also identified as regions responsible for successful encoding. Importantly, these regions were also involved during the testing phase, suggesting that participants could also learn from testing without feedback and re-study. Furthermore, Liu et al., (2014) identified additional brain regions that are only activated during retrieval yet also predict subsequent correct recall.

Whilst I am currently seeking expert contribution to this section, here is a first summary.

Retrieval practice is an effortful process as compared to simple restudy. Consistently, neuroimaging studies have found greater neural activity during retrieval than during restudy (Wing et al., 2013). In addition, retrieval practice could also potentiate subsequent learning, which is associated with greater frontoparietal activity (Nelson et al., 2013). These results suggest that during retrieval practice, the co-activation of old and new memories might provide a unique opportunity to modify these representations and to facilitate memory updating.

Researchers have proposed a two-process account (Liu and Reder, 2016; Liu et al., 2018) for the testing effect that we look to exploit with learner outcomes. Learners undergo a re-encoding process through re-exposure to the correct answer after successful retrievals (post-retrieval re-encoding), in addition to the retrieval attempt process. This post-retrieval re-encoding process also involves metacognitive monitoring and self-evaluation (Bai et al., 2015; Zhang et al., 2018) and can further enhance testing-related benefits (Liu and Reder, 2016).

Ye et al., (2020) confirm this conclusion. It was described as an "elegant human study" Ye et al., (2020) examined the effects of retrieval practice on memory performance and neural responses. The results from a set of experiments show that retrieval practice strengthens new memories and reduces intrusions of old memories without suppressing the old memories. Interestingly, this was related to enhanced representations in medial prefrontal cortex, further supporting the idea that this region of the brain is important for memory integration and consolidation.

Ye et al., (2020) reported retrieval practice as superior for long-lasting memory, recalling more updated targets with shorter response times and showed fewer memory intrusions when compared to Restudy. Distinct patterns and brain regions for the Retrieval Practice and Restudy were identified. Correctly recalled items showed stronger target activation than did incorrectly recalled ones in the ventral temporal cortex (VTC) during restudy whereas retrieval practiced items that were later correctly recalled were associated with stronger target activation than incorrectly recalled ones in the medial prefrontal cortex (MPFC).

This finding suggests that successful memory updating may involve different representations under the Retrieval Practice and Restudy conditions. The greater association of MPFC representation with enduring retention is consistent with consolidation processes and suggests that retrieval practice improves updating by driving consolidation more successfully than does restudy.